The invention is directed to devices and methods for coating print media.
It is sometimes desirable to coat printed media with a film of clear flexible material. Such coatings can be formulated and applied to help protect the printed image, enhance the printed image or provide a more uniform gloss level across the entire media (including both printed and unprinted areas). Coatings are applied to print media by overlaying on the media a multi-layered web containing the coating material, and then applying heat and pressure to fuse the coating material to the media. The web typically includes a film/layer of coating material, a carrier (sometimes called a backing), a release layer in between the coating material and the carrier, and an adhesive layer on the coating material to help the coating material adhere to the paper or other print media.
In a conventional single side coating device such as the one illustrated in FIG. 1, a peel bar 2 protrudes slightly into media path 3 downstream from fuser 4 to apply pressure to coating material web 5. Web 5 is threaded through fuser 4 from a supply spool 6 to a take-up spool 7. Coating material web 5 and media sheet 8 are sandwiched together through fuser 4 with the coating material film part of web 5 facing print media sheet 8. Fuser 4 applies heat and pressure to the web/sheet sandwich to melt the adhesive layer and affix the coating material film to the print media, and to soften the release layer. The carrier portion of web 5 angles up off peel bar 2 to take-up spool 7. The point pressure applied by peel bar 2 to web 5 helps the carrier portion of web 5 separate more cleanly from the coating film.
As the adhesive/coating material cools downstream from fuser 4, it cures to become permanently affixed to the print media. It is desirable that the adhesive/coating material cure as much as possible before the carrier is peeled away from the coating material. The more the adhesive/coating material cures before peeling, the better it will adhere to the print media and the less likely peeling will disturb the bond between the coating and the media. Conventional coating devices use only passive cooling. For passive cooling, the distance between the fuser and the peel bar must be long enough and the speed of the web slow enough to allow for the desired cooling.
Various embodiments of the present invention were developed in an effort to accelerate curing the coating material bond before peeling by actively cooling the web between the fuser and the peel bar. Accordingly, one embodiment of the present invention is directed to a print media coating device that includes a web supply, a web take-up, a fuser, and a web cooler downstream in the media path from the fuser. A coating material web runs from the web supply, along the media path through the fuser and the cooler, to the web take-up.
Another embodiment of the invention is directed to a method for coating print media that includes overlaying the print media with coating material, fusing the coating material to the print media, and after fusing, cooling the coating material.